关于列表元素修改

列表元素为AtomicLong时，会改变：

import java.util.ArrayList;
import java.util.Random;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.List;
import java.util.concurrent.atomic.AtomicLong;
import java.util.Collections;
public class test {
    public static void main(String[] args) {
        List<AtomicLong> a = new ArrayList<>(); 
        a.add(new AtomicLong(1));
        System.out.println(a.get(0).get()+"\n");
        AtomicLong b = a.get(0);
        b.compareAndSet(1, 2);
        System.out.println(a.get(0).get()+"\n");


    }
}

当列表元素为Interger时，不会发生改变：

import java.util.List;

public class test {
    public static void main(String[] args) {
        List<Integer> a = new ArrayList<>(); 
        a.add(1);
        System.out.println(a.get(0)+"\n");
        int b = a.get(0);
        b = 2;
        System.out.println(a.get(0)+"\n");


    }
}